At a rally supporting Hillary Clinton, Obama also urged senior Republicans to formally withdraw their endorsement of Mr Trump as presidential candidate.
Many top Republicans have however distanced themselves from Trump when a video in which he boasts of groping women surfaced.
Trump has however accused them of DISLOYALTY. He was particularly scathing about House Speaker Paul Ryan whom he described as a "weak and ineffective" leader.
Addressing a campaign rally in Greensboro, North Carolina, on Tuesday evening, Obama referred to Trump's crude remarks about women, saying: "Now you find a situation in which the guy says stuff that nobody would find tolerable if they were applying for a job at 7-Eleven."
He said: "You don't have to be a husband or a father to say that's not right. You just have to be a decent human being."
Obama questioned how senior Republican politicians could still want Mr Trump to be president.
"The fact is that now you've got people saying: 'We strongly disagree, we really disapprove... but we're still endorsing him.' They still think he should be president, that doesn't make sense to me," he told the crowd.